Vibrio cholerae, the causative agent of the worldwide health pandemic cholera, uses both quorum sensing (QS) and cyclic di-GMP (c-diGMP) to regulate biofilm formation and virulence. QS is a process by which bacteria secrete small, chemical signals to count their numbers in a population and control group behavior accordingly. c-diGMP is a recently discovered second messenger intracellular signaling molecule ubiquitous in bacteria. I have recently discovered a novel connection between QS and c-diGMP in V. cholerae. To answer some of the fundamental question about c-diGMP, and further understand its connection to QS, this research proposes to: Aim 1. Identify the transcriptional components that couple c-diGMP to alterations in gene expression using genetic screens;Aim 2. Identify specific ligands of GGDEF/EAL proteins in V. cholerae using bioinformatics and a high-throughput chemical screen;and Aim 3. Utilize X-ray crystallography to determine how signal recognition by GGDEF and EAL proteins modulates enzymatic activity. As both QS and c-diGMP control virulence in V. cholerae and numerous other bacteria pathogens, it is my hope that this work could lead to novel therapeutic approaches for the treatment of bacterial disease. 'Bacteria sense multiple small chemical signals to adapt and respond to their environment. These chemical signals are often control the ability of bacteria to cause disease. My research in Vibrio cholerae seeks to unravel the nature of these signals, and how bacteria respond to them, to develop novel therapeutic approaches to treat bacterial infections. RELEVANCE (See instructions): The K22 Research Scholar Development Award will allow me to support members of my laboratory (graduate students, technician, and/or post-docs) during the first two years of my new faculty position. This will allow me to develop research projects that will form the basis of one or more R01 grants.